<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* 清除默认样式 */
        * {
            margin: 0;
            padding: 0;
        }

        ul,
        ol {
            list-style: none;
        }

        .lunbo {
            position: relative;
            width: 880px;
            height: 550px;
            border: 1px solid #333;
            margin: 20px auto;
        }

        .lunbo .pic li {
            position: absolute;
            left: 0;
            top: 0;
            width: 880px;
            height: 550px;
            display: none;
        }

        .lunbo .pic .current {
            display: block;
        }

        /* 按钮 */
        .lunbo .btn a {
            position: absolute;
            top: 50%;
            width: 40px;
            height: 40px;
            margin-top: -20px;
            background-color: rgba(255, 255, 255, 0.3);
            font: 20px/40px "宋体";
            text-align: center;
            color: #fff;
            text-decoration: none;
            font-weight: bold;
        }

        .lunbo .btn .leftbtn {
            left: 20px;
        }

        .lunbo .btn .rightbtn {
            right: 20px;
        }

        .lunbo .btn a:hover {
            background-color: rgba(255, 255, 255, 0.6);
        }

        /* 下标 */
        .lunbo .sub {
            position: absolute;
            left: 100px;
            bottom: 50px;
            width: 240px;
        }

        .lunbo .sub li {
            float: left;
            width: 20px;
            height: 20px;
            margin-right: 20px;
            background-color: rgba(255, 255, 255, 0.4);
            font: 12px/20px "微软雅黑";
            text-align: center;
            color: #666;
            border-radius: 10px;
            cursor: pointer;
        }

        .lunbo .sub .current {
            background-color: #fff;
        }
    </style>
</head>

<body>
    <!-- 轮播图大结构 -->
    <div class="lunbo">
        <!-- 图片部分 -->
        <ul class="pic" id="pic">
            <li class="current"><img src="images/lunbo/c1.jpg"></li>
            <li><img src="images/lunbo/c2.jpg"></li>
            <li><img src="images/lunbo/c3.jpg"></li>
            <li><img src="images/lunbo/c4.jpg"></li>
            <li><img src="images/lunbo/c5.jpg"></li>
            <li><img src="images/lunbo/c6.jpg"></li>
        </ul>
        <!-- 按钮 -->
        <div class="btn">
            <a href="javascript:;" class="leftbtn" id="leftbtn">&lt;</a>
            <a href="javascript:;" class="rightbtn" id="rightbtn">&gt;</a>
        </div>
        <!-- 小圆点 -->
        <ol class="sub" id="sub">
            <li class="current">1</li>
            <li>2</li>
            <li>3</li>
            <li>4</li>
            <li>5</li>
            <li>6</li>
        </ol>
    </div>
    <script>
        var pic = document.getElementById("pic");
        var ullis = pic.children;
        var leftbtn = document.getElementById("leftbtn");
        var rightbtn = document.getElementById("rightbtn");
        var sub = document.getElementById("sub");
        var ollis = sub.children;
        // 设置全局信号量
        var idx = 0;
        // 1、右按钮点击事件，播放下一张图片
        rightbtn.onclick = rightScroll;
        // 2、左按钮事件，播放上一张图片
        leftbtn.onclick = function () {
            idx--;
            if (idx < 0) {
                idx = ullis.length - 1;
            }
            change();
        };
        // 3、 点击下方小圆点， 显示对应的图片
        for (var i = 0; i < ollis.length; i++) {
            ollis[i].index = i;
            ollis[i].onclick = function () {
                idx = this.index;
                change();
            }
        }
        // 4、自动播放轮播图
        var timer;
        timer = setInterval(rightScroll, 2000);
        // 5、鼠标移上事件，停止自动播放轮播图
        pic.onmouseover = function () {
            clearInterval(timer);
        };
        // 6、鼠标移出事件，再次进行自动播放轮播图
        pic.onmouseout = function () {
            timer = setInterval(rightScroll, 2000);
        };

        function rightScroll() {
            idx++;
            if (idx > ullis.length - 1) {
                idx = 0;
            }
            change();
        }

        function change() {
            for (var i = 0; i < ullis.length; i++) {
                ullis[i].className = "";
                ollis[i].className = "";
            }
            ullis[idx].className = "current";
            ollis[idx].className = "current";
        }
    </script>
</body>

</html>